Home > Maths > Reading People's Minds

By: Suzanne Elvidge BSc (hons), MSc - Updated: 27 Aug 2012 | Maths can't really reveal the secret of telepathy (reading people's minds), but some clever maths tricks make it seem like it is possible. Some of these will need a calculator. Examples are in square brackets but try them with other numbers and read people's minds!

• Think of a whole number (an integer) bigger than zero [e.g. 4]
• Square it (multiply it by itself) 
• Add the original number 
• Divide by the original number 
• Take away the original number 
• Divide by six 
• The answer is always three.

• Think of a whole number bigger than zero [e.g. 2]
• Multiply it by two 
• Divide by two 
• Take away the original number 
• The answer is always five.

#### Guess Two Numbers

• Pick a number from one to nine [e.g. 8]
• Double it 
• Multiply by five 
• Pick another number from one to nine and add it [e.g. 2 - 107]
• To guess the two numbers, subtract 25 from the total  – the first digit is the first number and the second digit is the second number.

#### The Grey Elephant From Denmark

• Pick a number from five to nine [e.g. 9]
• Take away five 
• Multiply by three 
• Square the number (multiply it by itself) 
• If the answer is higher than ten, add the digits together to get a single number [1+4+4=9).
• If the resulting number is less than five, add five – if it is more than five, subtract four 
• Multiply by two 
• Subtract six 
• Pick the letter of the alphabet that corresponds with the number (e.g. A=1, B=2)
• Pick a country beginning with the letter
• Pick a animal that begins with the second letter of the country
• What colour is the animal?
• This doesn't work every time, but most people will be thinking about a grey elephant from Denmark. Why? The answer to the numbers part is always four, so the letter chosen is always 'D'. Most people seem to choose 'Denmark' and a grey elephant.

#### Guess a Three Digit Number

• Pick a three digit number [e.g. 123]
• Multiply by seven 
• Multiply by 11 
• Multiply by 13 
• The answer will be the original number twice.

#### Guess the Date

• Pick a date [e.g. 1 January 2009]
• Add 18 to the chosen month 
• Multiply by 25 
• Subtract 333 
• Multiply by eight 
• Subtract 554 
• Divide by two 
• Add the chosen day 
• Multiply by five 
• Multiply by 20 
• Add the last two digits of the chosen year 
• Subtract 32940 
• The answer is the date in month/day/year format

#### Guess the Seven Digit Number

• Pick a seven digit number [e.g. 1234567]
• Multiply the first three digits by 80 
• Multiply by 250 
• Add the last four digits of the chosen number 
• Add the last four digits of the chosen number again 
• Subtract 250 
• Divide by two 
• The answer is the original number

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